prometheus-ecs-discovery not able to discover targets on EC2 with disabled DNS hostnames

[zsaurabhsabharwal]

On EC2 machines with DNS hostnames disabled, this check fails and as a result returns without processing that particular task.

This can be fixed by removing this check completely and instead extracting the IP address directly from EC2 instance description.

 ip = *t.EC2Instance.PrivateIpAddress

[chicofranchico]

What will happen if the instance has more than one private IP address? (also, could you update the code reference? I think it got messed up with latest merges)